When continuously printing by means of a rotary printing machine on a web of heavy stock material, such as packaging cartons used, for example, for boxes retaining foods, such as cereals or small boxes, such as medicines, toothpaste or the like, the problem arises that the heavy stock material varies substantially in size and the repetition rate of the printed material, likewise, varies widely. Thus, it is desirable to install printing cylinders, which may be composites such as a plate cylinder-blanket cylinder printing couple, in which the printing cylinders or a cylinder couple can be easily exchanged for cylinders of a different size. It has been customary, heretofore, when exchanging cylinders, to slide them out in a direction axially with respect to the cylinder shafts, and then place the cylinder on a cart or dolly. The cylinders are heavy. A blanket cylinder-printing cylinder couple of the type to which the present invention relates may well weigh over two tons.